An engine of a vehicle supplies lubricating oil to the journals of a crankshaft in order to lubricate the crankshaft. A conventional engine block arrangement is shown in FIGS. 7 to 9 wherein an engine 102 has a lower case 108 fixed to the lower side of a cylinder block 104 by setting bolts 110 so as to rotatably support therebetween a journal 106 of a rotatable crankshaft. A block-side bolt hole 112 is formed at the lower side of the cylinder block 104. The lower part of the block-side bolt hole 112 is smoothly formed, and the upper part is formed with internal threads so as to threadably engage the upper end of the setting bolt 110. A case-side bolt hole 114 passes vertically through the lower case 108 in alignment with the block-side bolt hole 112. Therefore, the lower case 108 is fixed to the lower side of the cylinder block 104 by inserting the setting bolts 110 into the block-side bolt holes 112 through the case-side bolt holes 114. In this arrangement, the crankshaft journal 106 is rotatably supported between the block-side journal bearing surface 116 of the cylinder block 104 and the case-side journal bearing surface 118 of the lower case 108 through block-side and case-side crank bearings 120 and 122, respectively.
A main gallery 124 serving as a lubricating-oil channel for circulating oil and extends in the longitudinal direction of the engine 102 generally parallel with the axis 115 of the crankshaft (not shown).
An oil channel 128 is linearly formed in the lower case 108 and communicates the main gallery 124 with a case-side oil groove 126 opening at the upper side of the case-side crank bearing 122 along the back or outer side thereof. Therefore, one of a plurality of the oil channels 128 linearly points to each of the crank journals 106 from the main gallery 124 as shown in FIG. 9. A block-side oil groove 130 is formed at the lower side of the cylinder block 104 and communicates with each case-side oil groove 126 and extends along the back or outer side of each block-side bearing 120. A plurality of oil passing holes 132 are formed in each block-side crank bearing 120 so as to introduce the oil from the respective block-side oil groove 130 into the respective crank journal 106.
In FIGS. 7 and 9, 134 denotes a knock-pin, 136 denotes a blow-by gas channel also serving as an oil dropping channel, 138 denotes an oil-filter setting portion, and 140 denotes an oil-cooler setting portion.
However, because oil is supplied to the crank journals from the main gallery through oil channels, a problem occurs in that foreign matters such as chips and cast sand left in the main gallery flow into the crank journals and damage the crank bearings or cause seizing.